Hot water storage tank with replaceable liner

ABSTRACT

A fluid storage tank comprising a main body and covers to close off openings of the main body. The main body and covers have inside surfaces which are, in use, in contact with fluid stored in the tank the main body is made up of a casing and a liner which is provided inside the casing. The covers are releasable retained in place and seal with the inside surface of the main body so that fluid can be stored in the tank.

DESCRIPTION

The present invention relates to a fluid storage tank. The fluid storagetank is used to store fluid which is under pressure.

The fluid storage tank of the present invention may be used as the hotwater storage tank in a hot water system. The hot water system may, forexample, be a solar, gas or electric hot water system. The fluid storagetank of the present invention may be used in other applications in whichfluid is stored under pressure in a tank or similar container, eg waterfilters, fire extinguishes, and gas cylinders.

FIELD OF THE INVENTION

Fluid storage tanks used to store fluid under pressure may deteriorateover time.

In fluid storage tanks used in hot water systems, deteriorationgenerally occurs to the lining inside such tanks which is in contactwith the fluid stored in the tank. However, due to the structure ofconventional tanks when this deterioration occurs to the lining, theentire tank must be replaced.

In contrast the present invention provides a fluid storage tank in whichonly the liner needs to be replaced if it deteriorates. In this way thefluid storage tank of the present invention is recyclable or renewable.

The present invention provides a fluid storage tank which may also beused in other applications in which fluid is stored under pressure toprovide a fluid storage tank which is recyclable or renewable.

SUMMARY OF THE PRESENT INVENTION

In accordance with one aspect of the present invention there is provideda water heater tank comprising: a cylindrical shell, closed at each ofits two ends by a releasable and removable curved end wall concentricwith and sealingly engaged within said cylindrical shell wall thereby toenclose an interior volume in which to store hot water; a cylindricalliner, separable from the shell, extending at least substantiallybetween the two ends of the shell and conforming there-through with theinside surface of the shell; an end wall support member adapted torestrain each end wall against movement induced by a force acting uponit as a result of above-atmospheric pressure in the tank interiorvolume, the end wall support member including both a central portion anda flange portion, the end wall support member central portion beingconcentric with both the end wall and the cylindrical shell, the endwall support member central portion conforming at least substantiallywith a surface of a central portion of the end wall facing away from thetank interior volume, while the flange portion extends from theperiphery of the end wall support member central portion in a directionboth away from the end wall at the other end and parallel to andconforming with the cylindrical shell wall; retention means to retaineach end wall support member in juxtaposition with a respective one ofthe ends of the cylindrical shell, the retention means being cooperativebetween the flange portion of the end wall support member and a portionof the cylindrical shell wall to which it conforms; wherein each endwall includes (a) a curved end wall center at least substantiallyconforming with the central portion of a respective cooperative one ofthe end wall supporting members and (b) a flange, coterminous with theperiphery of the end wall center and extending in a direction toward theend wall at the other end of the cylindrical shell wall, the end wallflange having a diameter to fit closely within the cylindrical shellwall and adjacently conforming liner and having sufficient flexibilityin a radial outward direction to increasingly compress, in response toincreasing internal pressure in the tank, a circumferentially extendingseal means cooperative between the end wall flange and the adjacentliner means supported by the cylindrical shell wall.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partly cross-sectional elevation view of a first embodimentof a fluid storage tank in accordance with the present invention;

FIG. 2 is a partly cross-sectional elevation view of the cover region ofthe fluid storage tank shown in FIG. 1;

FIG. 3 is a perspective view of the outside of the cover region of thefluid storage tank shown in FIG. 1;

FIG. 4 is a partly cross-sectional elevation view of the cover region ofa second embodiment of a fluid storage tank in accordance with thepresent invention;

FIG. 5 is a partly cross-sectional elevation view of a third embodimentof a fluid storage tank in accordance with the present invention;

FIG. 6 is a partly cross-sectional elevation view of a fourth embodimentof a fluid storage tank in accordance with the present invention;

FIG. 7 is a cross-sectional elevation view of the cover region of afifth embodiment of a fluid storage tank in accordance with the presentinvention; and,

FIG. 8 shows a particular embodiment of the casing and liner of a fluidstorage tank in accordance with the present invention.

DESCRIPTION OF THE INVENTION

FIGS. 1 to 8 and the description of the preferred embodiments use thesame reference numerals to denote the same parts. The description ofsuch parts is not repeated for subsequent embodiments, but it is to beunderstood that it applies in like manner to such subsequentembodiments.

In FIG. 1 there is shown a fluid storage tank 10 comprising a main body12 and covers 14 to close off the main body 12 near respective openingsthereof. The openings are located at respective ends of the main body12. The main body 12 has an inside surface 15a. The covers 14 each havean inside surface 15b. (The inside surfaces 15b of the covers 14 cannotbe seen in FIGS. 1 to 3 of the first embodiment of the fluid storagetank 10 since the covers 14 are not shown in cross-section in thoseFigures. However, the inside surface 15b of a cover 14' of the firstembodiment of the fluid storage tank 60 can be seen in FIG. 7). Theinside surfaces 15a and 15b are, in use, in contact with the fluidstored in the fluid storage tank 10.

The covers 14 seal with the inside surface 15a of the main body 12.

The main body 12 is substantially tubular.

The main body 12 comprises a casing 16 and a liner 18. The liner 18 isprovided inside the casing 16. The liner 18 is provided adjacent theinside surface of the casing 16. The liner 18 substantially conforms tothe inside surface of the casing 16.

Each cover 14 is provided with a seal at its outside surface 19. Thisseal may be in the form of an O-ring 20 which is positioned in a groove22 provided on the outside surface 19 of each cover 14. The O-ring seals20 of the covers 14 seal with the inside surface 15a of the main body12.

The O-ring seals 20 and grooves 22 are provided on respective portions24 of the covers 14 which lie adjacent the inside surface 15a of themain body 12. The liner 18 extends sufficiently far to the openings ofthe main body 12 that the O-ring seals 20 of the covers 14 seal with theliner 18 inside the main body 12. In this way the inside surface 15a ofthe main body 12 is defined by the inside surface of the liner 18. Thisis Each cover 14 comprises a portion 24 and a dome like portion 26. Theportion 24 is drum like, or tubular. Retaining means is provided toretain each cover 14 releasably in position with the main body 12.

The retaining means enable the covers 14 to be releasably retained inposition without connecting the covers 14 to the main body 12. The only"interaction" between the main body 12 and the covers 14 is the sealingcontact between the O-ring seals 20 and the portions 24 of the covers 14with the inside surface 15a of the main body 12. This is a pressureinduced sealing contact as will be later herein described.

The retaining means is shown in more detail in FIGS. 2 and 3.

In FIGS. 2 and 3, the retaining means is shown as comprising respectivecover retention members 28 which are fixedly secured to the main body 12at respective ends thereof adjacent the covers 14. The cover retentionmembers 28 are fixedly secured to the main body 12 by nuts and boltsshown at 30.

Each cover retention member 28 comprises a plate like portion 32, aperipheral strip like portion 33 and strengthening ribs 34. At least theinside surface 35 of the plate like portion 32 is shaped to conform tothe shape of the outer surface 19 of the dome like portion 26 of a cover14. The plate like portion 32 may itself be dome like. The peripheralstrip like portion 33 extends around the periphery of the plate likeportion 32 and projects therefrom away from cover 14. The strip likeportion 33 conforms with the shape of the inner surface 15a of the mainbody 12. The strengthening ribs 34 extend between the plate like portion32 and the peripheral strip like portion 33, at spaced intervals, asbest seen in FIG. 3. The bolts 30 pass through the strip like portions33 and the main body 12 to secure the cover retention members 28 to themain body 12. In FIG. 2 a gap is shown between the outside surface 19 ofthe dome like portion 26 of the cover 14 and the inside surface 35 ofthe plate like portion 32. However, this is only for clarity ofrepresentation. In practice, no such gap would exist.

FIG. 4 shows a second embodiment of a fluid storage tank 38 inaccordance with the present invention. The fluid storage tank 38 is thesame as the fluid storage tank 10 of the first embodiment except that itemploys an alternative arrangement for securing the cover retentionmembers 28 to the main body 12.

In the fluid storage tank 38, the nuts and bolts 30 are not used.Instead, the end portions of the casing 16 are turned over the edges ofthe strip like portions 33 of the cover retention members 28 to form aturned lip 39. The cover retention members 28 are in this way fixedlysecured to the casing 16 of the main body 12 by a clamping type actionof the turned lip 39.

The remainder of the fluid storage tank 38 is the same as the fluidstorage tank 10.

FIG. 5 shows a third embodiment of a fluid storage tank 40 in accordancewith the present invention. The fluid storage tank 40 is similar to thefluid storage tank 10 of the first embodiment except that it employs adifferent arrangement of the retaining means to retain the covers 14 inposition.

In the fluid storage tank 40, the retaining means comprises the coverretention members 28 of the fluid storage tank 10, but these are notsecured to the main body 12.

Instead, there is provided an elongate bolt 42 which extends through themain body portion 12 between the covers 14. The covers 14 and coverretention members 28 are provided with appropriate holes for the bolt 42to pass therethrough and nuts 44 are provided outside the tank 40 tokeep the bolt 42 in position. The nuts 44 are provided on the outside ofeach pair of covers 14 and cover retention members 28.

The remainder of the fluid storage tank 40 is the same as the fluidstorage tank 10.

FIG. 6 shows a fourth embodiment of a fluid storage tank 50 inaccordance with the present invention. The fluid storage tank 50 issimilar to the fluid storage tank 10, except that it employs a differentarrangement of the retaining means to retain the covers 14 in position.

Once again, the retaining means comprises the cover retention members 28of the fluid storage tank 10, but these are not secured to the main body12.

The fluid storage tank 50 is provided with a flue-way 52 extendingthrough the main body 12 between the covers 14. Securing means (notshown) are provided outside the fluid storage tank 50 adjacent the coverretention members 28 in a similar manner to the nuts 44 of the fluidstorage tank 40.

Thus, the fluid storage tank 50 is of a similar structure to the fluidstorage tank 40, except that the bolt 42 of the fluid storage tank 40 isreplaced by a flue-way 52 and the nuts 44 are replaced by analternative, but analogous, form of securing means. The remainder of thefluid storage tank 60 is the same as the fluid storage tank 10.

FIG. 7 shows the cover region of a fifth embodiment of a fluid storagetank 60.

Whilst in FIG. 7 only one end of the fluid storage tank 60 is shown, itwill be understood that the other end is of a similar form.

The fluid storage tank 60 is similar to the fluid storage tank 10 exceptthat it employs an alternative sealing arrangement of the covers 14'with the inside surface 15a of the main body 12.

The covers 14' of the fluid storage tank 60 do not use the O-ring seal20 and groove 22 of the covers 14 of the previously describedembodiments.

In the fluid storage tank 60, each cover 14' is formed with an outwardlyextending sealing flange or lip like portion 62 at the outside surface19 at the peripheral edge of the portion 24. This portion 62 is tapered,as can be seen in FIG. 7. The portion 62 seals with the inside surface15a of the main body 12.

The fluid storage tank 60 may employ retaining means of the same type asany of the fluid storage tanks 10, 38, 40 and 50.

The remainder of the fluid storage tank 60 is the same as the fluidstorage tank 10.

In the fluid storage tank of the present invention, the liner 18 may bein the form of a membrane, coating, ceramics material, or a tubularinsert which fits into the casing 16.

The liner 18 may be made of material which is non-corrodable since thecontents of the fluid storage tank will be in contact with the liner 18.Depending upon the application of the fluid storage tank of the presentinvention, the liner 18 may need to be made of material which is alsohigh temperature resistant, e.g. when the fluid storage tank is used asthe storage tank in a hot water system.

The liner 18 may be made of a plastics polymer. The use of a plasticspolymer is particularly suitable when the liner 18 is in the form of atubular insert.

The covers 14, 14' are also preferably made of a material which isnon-corrodable (and high temperature resistant if required) since thecontents of the fluid storage tank will also be in contact with theinside surfaces 15b of the covers 14, 14'.

The covers 14, 14' may be made from a plastics material, e.g. plasticspolymer.

If the covers 14, 14' are not made from a non-corrodable (and hightemperature resistant) material, then their inside surfaces 15b areprovided with a non-corrodable (and high temperature resistant) coatingor lining. The casing 16 may be made from metal, e.g. steel. The casing16 surrounds and encloses the liner 18.

Similarly, the cover retention members 28 retain the covers 14, 14' inposition. In this way, the casing 16 and the cover retention members 28support the liner 18 and the covers 14, 14', respectively, and carry thestructural stress from the fluid stored by the fluid storage tank of thepresent invention.

The embodiments of the fluid storage tank that have been describedherein incorporate retaining means which comprise cover retentionmembers 28 having plate like portions 32 conforming to the shape of theouter surface 19 of the dome like portions 26 of the covers 14, 14'. Itis these plate like portions 32 which carry the structural stress fromthe fluid pressing against the covers 14, 14'. However, if the covers14, 14' are made of a material of sufficiently high strength, the coverretention members 28 may be omitted, or modified. Accordingly, in theembodiments shown in FIGS. 5 and 6, the cover retention members 28 may,in such cases, be omitted. In the embodiments shown in FIGS. 1 to 4, thecover retention members 28 may, in such cases, be modified so that theplate like portions 32 are omitted. This then leaves only the strip likeportions 33 which are secured to the casing 16 and which are modified toengage with the covers 14, 14'. In this way, the covers 14, 14' willstill be retained in position.

Depending upon its application, appropriate holes (not shown) forfittings and the like (not shown) may be provided in the covers 14, 14'and cover retention members 28. In the case of the fluid storage tankbeing used in a hot water system, such holes accommodate fittings suchas the fluid inlet and outlet pipes. The casing 16 may be formed from astrip material which is wound into a helix structure and has itsabutting edges butt-welded together.

A casing of this type is shown in FIG. 8 and is identified by referencenumeral 16'.

The casing 16' is formed from strip material 72 whose butt-weldedhelical edges are shown by the helical line 74.

A casing 16' formed in this way is particularly suitable when the fluidstorage tank is used for a hot water system. However, it may also beused for other applications of the fluid storage tank. The use of acasing 16' in the form shown in FIG. 8 is particularly suitable when theliner 18 is in the form of a tubular insert. This is also shown in FIG.8. A liner in the form of a tubular insert is identified in FIG. 8 byreference numeral 18'. The liner 18' is fitted into a casing 16' made ofstrip material 72 and may have an outer diameter that is very slightlygreater than the inner diameter of the casing 16' such that the liner18' cannot readily be inserted into the casing 16. This liner 18' isfirst placed into a freezer to reduce its temperature. The temperatureof the liner 18' is reduced sufficiently such that it shrinks in itsradial direction, i.e. the diameter of the liner 18' is reduced. Thisreduction of its diameter needs to be only a few millimeters. Subjectingthe liner 18' to a temperature of minus 20° C. for approximately 24hours results in sufficient reduction.

After the appropriate time, the liner 18' is removed from the freezerand is then pushed into the casing 16'. This temperature reduction ofthe liner 18' also results in the liner 18' being inwardly pre-loaded.

As the liner 18' returns to ambient temperature, it expands. In sodoing, the outer surface of the liner 18' tightly bears against theinner surface of the casing 16'.

The casing 16, 16' of the present invention carries the structuralstress from the fluid contents inside the fluid storage tank. Even inthe case of the liner 18 being in the form of a tubular insert, this isalso the case.

The fluid storage tank of the present invention is recyclable orrenewable. This means that if defects occur in the liner 18, 18' it canbe replaced.

This can be done by draining the contents of the fluid storage tank andreleasing the retaining means which retains the covers 14, 14' inposition. Depending upon the form of the liner 18, 18', the liner 18,18' can be then removed from the casing 16, 16' and replaced. This isparticularly suitably in the case of the liner 18' being in the form ofan insert.

If the liner 18 is in the form of a coating, or the like, on the insidesurface of the casing 16, 16' then a new coating can be applied or thecasing 16, 16' and lining 18 are both removed and replaced as a unit. Inanother alternative embodiment, the main body 12 may further comprise a(tubular) sleeve (not shown). This sleeve is inserted into the casing16, 16' to lie adjacent the inside surface of the casing 16, 16'. Theliner 18, 18' is then provided adjacent the inside surface of thesleeve.

The sleeve can be used with any form of liner 18, 18' and isparticularly suitable when the liner 18 is in the form of a coating orthe like.

The sleeve may be made of an insulating material, e.g. urethane.

When the liner 18, 18' becomes defective, the sleeve along with theliner 18, 18' may be removed as a unit from the casing 16 and replaced.

Thus, the form of the main body 12 and releasably retained covers 14,14'(which are not connected to the main body 12) of the fluid storage tankof the present invention allow the fluid storage tank of the presentinvention to be recyclable or renewable.

Whilst the embodiments of the fluid storage tank of the presentinvention have been described with reference to particular forms of thesealing arrangement (viz. O-ring seals 20 and flange or lip likeportions 62), covers 14 and retaining means of any suitable form may beused. The fluid storage tank of the present invention can be used tostore fluid under pressure.

The pressure exerted by the fluid contents of the fluid storage tank ofthe present invention exerts outwardly directed radial and longitudinalforces on the fluid storage tank.

The longitudinal forces are countered by the retaining means, or covers14,14'. The retaining means prevent the covers 14,14' from moving in theoutward direction, i.e. away from one another. At the same time, theradial forces exerted by the contents of the fluid storage tank push thedrum like portions 24 of the covers 14, 14' in a radial direction tobear against the inside surface 15a of the main body 12. This pushes theseal means, e.g. the O-ring seals 20 or the sealing flange or lip likeportions 62, into closer contact with the inside surface 15a (ie. theliner 18) of the main body 12 thus providing a stronger seal withincreasing pressure of the fluid in the fluid storage tank.

Whilst in the embodiments hereindescribed, the fluid storage tank of theembodiments is shown as having a pair of covers 14, 14' which arereleasably positioned to cover a respective opening, it is possible thatonly one of the covers 14, 14' is releasably retained and the othercover 14, 14' is fixedly retained at one end, i.e. fixed to the mainbody 12. This may be done by directly connecting the cover 14, 14' tothe casing 16, e.g., by a metal strap or by fixedly connecting asecuring means of the retaining means to the casing 16.

In the case of the fluid storage tank of the present invention beingused in a hot water system, e.g. a solar, gas, or electric hot watersystem, the fluid storage tank encloses a space which is suitable tocontain potable water, e.g. drinking water.

In other applications, the fluid storage tank would store theappropriate fluid, e.g. gas in a gas cylinder application, etc.

Modifications and variations such as would be apparent to a skilledaddressee are deemed within the scope of the present invention.

We claim:
 1. A water heater tank comprising:a cylindrical shell, closedat each of its two ends by a releasable and removable curved end wallconcentric with and sealingly engaged within said cylindrical shell wallthereby to enclose an interior volume in which to store hot water; acylindrical liner, separable from said shell, extending at leastsubstantially between said two ends of said shell and conformingtherethrough with the inside surface of said shell; an end wall supportmember adapted to restrain each said end wall against movement inducedby a force acting upon it as a result of above-atmospheric pressure insaid tank interior volume, said end wall support member including both acentral portion and a flange portion, said end wall support membercentral portion being concentric with both said end wall and saidcylindrical shell, said end wall support member central portionconforming at least substantially with a surface of a central portion ofsaid end wall facing away from said tank interior volume, while saidflange portion extends from the periphery of said end wall supportmember central portion in a direction both away from said end wall atthe other end and parallel to and conforming with said cylindrical shellwall; retention means to retain each said end wall support member injuxtaposition with a respective one of said ends of said cylindricalshell, said retention means being cooperative between said flangeportion of said end wall support member and a portion of saidcylindrical shell wall to which it conforms:wherein each said end wallincludes (a) a curved end wall center at least substantially conformingwith said central portion of a respective cooperative one of said endwall supporting members and (b) a flange, coterminous with the peripheryof said end wall center and extending in a direction toward the end wallat the other end of said cylindrical shell wall, said end wall flangehaving a diameter to fit closely within said cylindrical shell wall andadjacently conforming liner and having sufficient flexibility in aradial outward direction to increasingly compress, in response toincreasing internal pressure in said tank, a circumferentially extendingseal means cooperative between said end wall flange and said adjacentliner means supported by said cylindrical shell wall.
 2. A water heatertank as claimed in claim 1 in which said seal means comprises aresilient ring interposed between said end wall flange and said liner.3. A water heater tank as claimed in claim 2 in which said resilientring is retained in a groove formed around the periphery of said endwall flange.
 4. A water heater tank as claimed in claim 1 in which saidseal means comprises a radially outwardly protruding, circumferentiallyextending, ridge integral with said end wall flange adapted to create aseal by locally increasing force induced by internal pressure in saidtank around a line of contact between said circumferentially extendingridge and said liner where said ridge and said liner make mutualcontact.
 5. A water heater tank as claimed in claim 1 in which saidretention means is selected from the group consisting of pluralremovable connections and plural breakable connections between said endsupport member flange portion and said cylindrical shell wall to enableremoval of both said end wall support members and end walls to gainaccess to said liner for removal thereof from said shell.
 6. A waterheater tank as claimed in claim 5 having plural removable connectionsthat are reusable for subsequent reassembly of said end support memberto said cylindrical shell wall.
 7. A water heater tank as claimed inclaim 6 in which said removable connections are threaded fastenerscircumferentially spaced around said cylindrical shell wall.
 8. A waterheater tank as claimed in claim 5 having plural breakable connectionsthat can be broken without impairment of said end support member or saidcylindrical shell for subsequent reassembly into a water heater tank. 9.A water heater tank as claimed in claim 8 in which said plural breakableconnections are spot welds circumferentially spaced around saidcylindrical shell wall.
 10. A water heater tank as claimed in claim 1 inwhich said retention means comprises an axial extension of at least oneof said ends of said cylindrical shell axially outwardly beyond theflange of said end support member together with a radially inwardlyextending structure contiguous with said axial extension being adaptedto restrain axially outwardly relative movement between said end supportmember and said shell in response to internal pressure in said tank. 11.A water heater tank as claimed in claim 10 in which said radiallyinwardly extending structure means comprises a radially and axiallyinwardly bent lip adapted to engage circumferentially the free end ofsaid flange portion, said lip formed by bending said axial extension ofsaid end of said cylindrical shell inwardly.
 12. A water heater tank asclaimed in claim 11 in which said bent lip is adapted to be straightenedif required to enable removal of both said end wall support members andsaid end walls to access said liner for removal thereof from said shell.